New Diet Studies, or How Fads are Born

The interaction of diet and health is immensely difficult to unravel. Flawed studies don’t help

How did the vaccine-avoidance cult get started? On the basis of a fraudulent study purporting to show a connection between MMR vaccination and autism. The author has since been barred from the scientific and medical communities.

How did the water fluoridation scare start? Remember the paranoid John Birch Society and the communist plots they detected in every corner of our life? Yes, it was they who darkly warned us about a communist plot to poison us with fluoride in our water.

I can go on and on, but the overall story is the same: Unscrupulous actors praying on an ignorant public.

Diets: Protein vs. Carbohydrates.

An article in Science in the News and Analysis section, titled “Diet Studies Challenge Thinking on Proteins Versus Carbs,”caught my attention. I am a real fan of studies that debunk received wisdom because that is how science makes progress, by skepticism, constant reexamination and revision of reigning theories.

The article reviews two studies published in Cell Metabolism. In one, an Australian group led by nutritional physiologist Stephen Simpson and biogerontologist David Le Couteur at the University of Sydney tried to clear up some of the confusion by assigning 858 mice to one of 25 diets with different mixes of protein, carbs, fats, and fiber. All were allowed to eat as much as they wanted.

The mice whose diets included 5% to 15% protein and 40% to 60% carbohydrates lived the longest, up to 150 weeks compared with 100 weeks for those on a diet of about 50% protein. The animals on the low-protein/high-carb plan also had lower blood pressure, better glucose tolerance, and healthier cholesterol. (Levels of fat in their diet didn’t seem to make much difference.) Mice that ate lots of protein were skinnier—just as people on high-protein diets tend to be. But for these mice, slender translated to ill health and earlier death.

The second study, led by gerontology researcher Valter Longo and graduate student Morgan Levine at the University of Southern California in Los Angeles, focused on data from 6381 adults over 50 years old who were interviewed once about their diet as part of NHANES, a national survey of health and nutrition. Longo’s team used death records to conclude that those under 65 whose self-reported diets they classified as high-protein—the participants said at least 20% of their calories came from protein—were at much higher risk of illness and death than a group who took in 10% or fewer of their calories from protein. The high-protein eaters were more than four times as likely to die from cancer over the 18 years after they were surveyed, and 75% more likely to die of any cause.

Guide to the bewildered: IGNORE!

These studies are so flawed that it is hard to know where to begin. It would also make for a boring minutely technical analysis. But here are the big ones.

Photo from bugmanrochester

Mice are not human. We cured mice of diabetes, hypertension, and cancer—and we made them live to a preternatural age. Why didn’t it translate to us afflicted humans? Because mouse physiology differs from human’s.

For one thing, they are constant feeders, we are not. Or at least, natural selection didn’t mean us to be; the ones who defy it are recognizable by their heft and are paying the price in the form of diabetes, hypertension, heart disease and cancer.

The investigators used one strain of mice, all of whom share a common genetic background. In other words, a highly artificial situation. Would other strains show the same results? Would wild-type mutts cooperate as nicely as the purebred? Were the mice allowed to exercise? After all, the caloric equation comprises of two terms: intake and output. The study completely neglects the latter. Enough said.

The second study doesn’t deserve as much comment. The study is based on an interview, yes one interview! How reliable are interviews in eliciting diet information? Totally not! And speaking of quality: There is no account taken of the quality of the food. Is protein from a MacDonald hamburger equivalent to fish protein? Sausage is mentioned in the text as a source of protein, but this has 79% fat and 21% protein (http://nutritiondata.self.com/facts/sausages-and-luncheon-meats/1375/2).

Americans on average take in about 16% of their calories from protein. So, according to these studies, we should live a very long life and rarely get cancer…would that be true.

The interaction of diet and health is immensely difficult to unravel. Flawed studies don’t help. But like the free radical theory of disease and longevity, when the public wants an easy answer, they acquire a life of their own and become dogma. We can only hope that these studies don’t get legs, as they say in the media.

Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.

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